1. References Cited
2,531,227 11/1950 Lubins
2,772,910 12/1956 Doyle
3,751,094 8/1973 Bohler
4,050,728 9/1977 Davidsort
4,264,096 4/1981 Barnett
4,787,661 11/1988 Rutledge
4,944,541 7/1990 Waldschmidt
2. Discussion of the Prior Art
Although this invention is described herein in terms of "shovels", it will be recognized by one skilled in the art that it is equally applicable to other similar digging or lifting tools such as pitchforks, scoops, spades, rakes, hoes, etc.
The single-handled shovel has been in existence for many years. Simple, inexpensive, and versatile, this manually-operated ;Lifting tool comes in a variety of forms and sizes, and serves a multitude of industries. Though successful in the marketplace, the single-handled shovel by its design inevitably places the operator at risk of back-related injuries.
Designed to load, lift, and discharge loose :material from a location near the ground, the typical single-handled shovel consists of a blade that is attached to a long shaft. The shaft is commonly referred to as a handle, but in the following discussion the term "shaft" will be used to distinguish the elongated shaft portion of the shovel from the auxiliary handle of the invention, and from the "D" shaped handle which is often provided at the opposite end of the shaft from the shovel blade (particularly in snow shovels, pitchforks or the like).
The shaft is grasped by the operator with both hands to control displacement of the material that is accumulated within the contour of the blade. In the load phase of the shovel cycle where material is difficult to accumulate (scoop) and/or heavy, inadequate blade control leverage warrants placement of a hand near the blade, and consequently, deviation from an upright position. The load-accumulating scoop, or thrust of the blade into the material positions the loaded blade away from the body.
Here begins the lift phase whereby the operator, already bent over to improve lifting leverage, proceeds to simultaneously raise and reposition the loaded blade closer to the body. Lifting ceases when the operator proceeds to a posture sufficient for meeting discharge direction arid distance requirements. With a jerk of the arms and/or a twist of the back, the material slides off the blade, thus completing the shovel cycle.
Back effort can be minimized in a manual shoveling application if the operator can use the shovel while in a near or fully upright posture. This is the underlying principle in existing shovel designs that feature a bent single shaft (such as the Rugg Back-Savers), or those with a concave blade surface best suited for plow operations.
There have been patents issued over the years that claim reduction of shoveling back effort through use of an auxiliary handle. Such designs, however, have limitations that restrict or preclude market potential.
Doyle, U.S. Pat. No. 2,772,910, and Barnett, U.S. Pat. No. 4,264,096 show auxiliary handles of fixed length which cannot be adjusted to accommodate various shovel handle lengths, operator arm lengths and shoveling applications.
Lubins, U.S. Pat. No. 2,531,227, Bohler, U.S. Pat. No. 3,751,094, and Waldschmidt, U.S. Pat. No. 4,944,541 embody adjustable length in flexible positioning of the auxiliary handle, but incur a penalty of lower mechanical advantage.. These patents also demonstrate a limited range of auxiliary handle motion, and subsequently an awkward and/or uncomfortable shoveling operation.
In addition to featuring a complex clamping configuration, Davidson, U.S. Pat. No. 4,050,728 also claims a universal joint that makes a certain range of planar movement impossible.
Davidson, Barnett, Waldschmidt and Rutledge (U.S. Pat. No. 4,787,661) require modifications to the shovel for which the auxiliary handle is being attached.
Auxiliary handles featured in Barnett and Rutledge cannot be transferred to another shovel.
Lubins, Doyle and Davidson have no apparent feature to prevent slippage of the auxiliary handle clamp configuration relative to the shovel shaft.